STABILITY OF THE RELATIONSHIP BETWEEN SPECIFIC LEAF-AREA AND CARBON-ISOTOPE DISCRIMINATION ACROSS ENVIRONMENTS IN PEANUT

In previous experiments, specific leaf area (SLA) was shown to be correlated with both carbon isotope discrimination (Delta) and water use efficiency in peanut (Arachis hypogaea L.) suggesting that SLA can be used to screen genotypes for W. However, very little information is available on the stability of the relationship between SLA and Delta across environments. The present study was conducted to examine genotype x environment (G x E) interaction for the relationship between SLA and Delta. Four peanut genotypes (Chico, McCubbin, Shulamit, and Tifton-8) with contrasting carbon isotope discriminating characteristics were grown in the field either under adequately irrigated or rainfed conditions at two locations in Queensland, Australia. The seasonal changes in Delta and SLA were examined by sampling leaves at monthly intervals. The values of Delta and SLA were significantly influenced by the location, genotype, and irrigation treatments. Genotype x location interaction effects on the relationship between Delta and SLA were not significant. The positive relationship between SLA and Delta was maintained when data were combined over sites and treatments (r(2) = 0.87, P < 0.01) indicating stability of the relationship across environments. The SLA was negatively correlated with nitrogen content per unit leaf area (SLN) which in turn was negatively correlated with Delta. The results suggested that SLA can be used as a surrogate for Delta.